A polymer PTC element which comprises a polymer PTC component formed, for example, in a laminar form from a conductive polymer material comprising a polymer material and conductive fillers contained therein, and metal electrodes placed on both sides of the polymer PTC component is widely used in electrical or electronic apparatuses.
Such a polymer PTC element is used in an electronic apparatus as, for example, a circuit protection device. It has substantially no resistance when the apparatus is in normal use. However, when the apparatus is in an abnormal state or when the environment around the apparatus is in an abnormal state, the temperature of the polymer PTC element itself becomes high, and the resistance of the element increases rapidly so as to cause a so-called trip, and thereby the element acts to prevent destruction of the apparatus beforehand by cutting off a current flowing through the apparatus. When the apparatus is functioning normally, such a polymer PTC element preferably has as low a resistance as possible as if the element were absent.
When using a polymer PTC element in an electronic apparatus, a polymer PTC element having metal electrodes connected to a polymer PTC component is obtained, then a PTC device having a lead electrically connected to at least one of the metal electrodes is obtained, and such PTC device is connected to a prescribed wiring or an electric component, so that the polymer PTC component is inserted into a prescribed circuit of the electronic apparatus via the lead.
The polymer PTC device comprising a lead is produced by affixing by thermal compression, for example, metal foils as metal electrodes on a top surface and a bottom surface of an electrically conductive polymer material extruded, for example, in a sheet form, cutting or punching out it into a prescribed size, then connecting various types of leads to the metal electrodes in order to insert the polymer PTC device in a circuit of an electronic apparatus. For example, in Japanese Patent Kokai Publication No. 2001-102039 , solder connection, resistance connection and the like are used to for the connection of the lead.